“OPEGUARD™” (produced by Senju Pharmaceutical Co., Ltd. and sold by Takeda Chemical Industries, Ltd.) and “BSS PLUS™” (imported and sold by Santen Pharmaceutical Co., Ltd.) are representative commercially available solutions used for intraocular and extraocular perfusion and washing in ophthalmic surgeries such as cataract surgery, vitreous surgery and glaucoma surgery. Among ophthalmic surgeries using such an ocular perfusion/washing solution, a representative method for cataract surgery, phacoemulsification is carried out by ultrasonically disrupting a clouded crystalline lens and aspirating the same using a “phacoemulsifier”.
More specifically, the surgery is carried out by breaking up a crystalline lens by mechanical impact (front-and-back vibrations) of a metal tip (such as an ultrasonic tip, a US tip, a phaco tip) that creates ultrasonic sound waves with the cavitation at the tip end, followed by aspirating the broken pieces of the lens through the tip, while a perfusate in an amount according to the amount of aspiration is supplied through a sleeve surrounding the tip so as to prevent the intraocular (anterior chamber) pressure from dropping due to the aspiration. Since the perfusate passes around such an US tip generating ultrasonic sound waves, numerous gas bubbles are generated in the solution due to the temperature rise and cavitation caused by the ultrasonic waves. The gas bubbles gather at the nodes in the standing wave and coalesce into large bubbles. When such bubbles are collapsed by the compressive force that acts on the solution, highly impactive acoustic energy is released into the solution and this energy transforms into shock waves, which act as part of the destructive force for disrupting the crystalline lens nucleus.
However, other gas bubbles that do not function as the above-mentioned force for destroying the nucleus but rather impair visibility around the tip region during the surgery may also occur, depending on the kind of perfusate used in the operation. That is, even when cavitation does not occur in the solution, the gas dissolved in the solution readily bubbles when the pressure drops below a certain level. Such gas bubbles do not generate acoustic energy high enough to produce a destructive force for disrupting the nucleus and rather impairs visibility during the surgery, thus having the disadvantage of impeding accurate visual inspection of the portion being operated on.
It is preferable that the perfusion/washing solution used in ophthalmic surgeries be prevented, as much as possible, from being accompanied by such bubbling that impairs visibility during the surgery.